1. Field of the Invention
The invention relates to an ignition system for an internal combustion engine having the following structure:
(a) a pulse generator generates synchronously with the rotation of the crankshaft angular pulses and one reference pulse;
(b) within a first angular interval of the rotation of the crankshaft, for the determination of a speed value, clock pulses are counted in a speed counter during a time basis and simultaneously a load value is converted to a multiple-bit value;
(c) according to the speed value and the load value a characteristic field storage, storing fixed values, is sampled;
(d) as a function of the storage values of the characteristic field storage an ignition counter is preset, which, by the counting of angular pulses, delivers a switching pulse for the ignition signal;
(e) the speed value and the load value are stored in buffers at the end of the time basis;
(f) the characteristic field storage contains multiple-bit ignition values for the determination of the ignition angle;
(g) to a given angular value the preadjustable ignition counter is preset with the specific multiple-bit ignition value.
2. Description of the Prior Art
An ignition system of the said type is adapted for internal combustion engines with spark ignition (Otto engines) as well as for internal combustion engine with auto-ignition (Diesel engines). In the first case the ignition signal is the voltage signal for the ignition plug, in the latter case the ignition signal is the trigger signal for the injection pump.
In the case of a prior art ignition system the ignition identification field is stored with a coarse speed screen and load screen. The specific ignition angle is gained by the transfer of the stored values of the ignition characteristic field into a microprocessor and by interpolation calculation. This ignition system comes to time limits due to the fact that at high speed the calculations cannot be carried out during the time available for a rotational period. That is particularly true if additional corrections of the ignition value shall be carried out as a function of the temperature and/or the fuel composition, in particular of the octane value.
An ignition system of the above mentioned kind is described in the DE-OS 28 45 024. A consideration of further characteristic values is not provided therein. However, it is evident that a basic characteristic field does not render possible optium engine operation.
The DE-OS 31 16 593 provides the adaption of a permanently stored basic characteristic field of specific engine data in that ignition values corrected in accordance with the individual engine are stored in a correction field, which is provided as read-write storage. This correction characteristic field adapted to a specific engine is then used as a characteristic field. Any adaptation of the storage values to engine characteristic values is not provided therein.